Krzyzowa, Poland — Striding down from the tiny "emperor station" near Schweidnitz in Lower Silesia (now in Poland, at one time Germany), Helmuth Caspar von Moltke arrives at Kreisau, a sprawling estate that is his birthplace and childhood home.

As he walks along a dirt path, this tall, elegant man feels the weight of responsibility to see to it that Kreisau, laden with personal memories and important history, be used to promote a peaceful, united Europe. It was this vision for which his father died: It was here that his father and a group of his friends met secretly to reject the Nazis and plot a democratic Germany as part of a united Europe without Adolf Hitler.

Those were dangerous, treasonous ideas in 1930s and '40s Germany. They led to prison and execution for most of those involved in the "Kreisau Circle."

In 1866, German Chancellor Otto von Bismarck had helped Mr. Moltke's great-great uncle, Field Marshal Count Bernhard von Moltke, acquire the estate, a thank-you for help in winning a war against Austria.

As children, Caspar and his brother, Konrad, would wait eagerly for the steam engine train to puff up to the emperor station. It wasn't until much later that they learned what went on at Kreisau: Their father, Helmuth James von Moltke, had gathered his friends there to plan for a new Germany without the "Führer."

After the Allied victory in 1945, Germans were driven out of Silesia; and Moltke's home, renamed Krzyzowa and now part of Poland, fell into ruin. But the Kreisau story did not end. It only slept during the years when his mother, Freya, took her two young sons first to Switzerland, then to South Africa and eventually Britain.

Slowly, appreciation for the Moltke legacy was reborn. Inspired by Helmuth James, individuals in Poland and East Germany vowed to turn crumbling Kreisau into a "New Kreisau," an international meeting place for young people. Freya became honorary chair of the New Kreisau Center for European Mutual Understanding.

Moltke took over that role upon his mother's death two years ago. A retired lawyer, he lives in Montreal and New England with his wife, but works intensely for the New Kreisau. "We have our property back, but in a different way," he says. "It is now serving a useful purpose."

Thousands of youths from Germany to Ukraine, Belarus to Afghanistan, converge on Kreisau each year to participate in workshops designed to continue the Moltke family's legacy – the protection of human rights and advocacy for democracy and tolerance.

Hitler no longer endangers Europe. But the extremism ignited by Europe's current economic upheavals could. Passing on his parents' ideals represents the best way there is to "inoculate" young people today against extremist ideology, Moltke says.

As the most visible spokesperson for Kreisau, Moltke epitomizes the ability of former enemies – Germany and Poland – to turn hatred into reconciliation. "A lot of terrible history happened between Russia and Poland, and between Germany and Poland," says Moltke, who was 6 years old when Hitler's Gestapo (secret police) hanged his father.

For more than a century until the Treaty of Versailles in 1918, Russia, Prussia, and Austria had repeatedly divided and reconfigured Poland between themselves. Later, Nazi Germany made no secret of its intention to erase Poland and its people from the map. As a border region between Poland and Germany, Lower Silesia symbolized the deep tensions between the two countries long after it was given to Poland in 1945. There, Poles' distrust and fear of Russia and Germany remained deeply anchored.

Then in the months before the Berlin Wall came down in 1989, a small group of Polish and East German intellectuals and theologians drew inspiration and strength from the story of Kreisau in their own struggle to build a new post-communist Europe.

"Helmuth James struggled with how to think freely, and to think about a new Europe in a context [under Hitler] where it wasn't possible to think freely," says Wolfram Bürger, a theology student in East Germany and now a pastor in Berlin. "He rethought Europe at a time when there was no hope that Europe could ever have a positive future.

"For us, young theology students, that was a mind-boggling thing," says Mr. Bürger, who led the move to create the nonprofit New Kreisau Center. "In a context of a deeply anchored status quo of the East-West divide, to be thinking in terms of beyond this divide was revolutionary."

On Nov. 12, 1989, three days after the Berlin Wall came tumbling down, Poland's Tadeusz Mazowiecki, who had just become the first noncommunist head of government in Eastern Europe, and then-German Chancellor Helmut Kohl chose Kreisau to hold a celebration of a reconciliation mass between their countries. They committed 30 million deutsch marks ($17 million) to restore the former Moltke estate.

Once she was reassured that Kreisau would be a European, not just a German, initiative, Freya backed the project. In the words of Jürgen Telschow, a lawyer in Frankfurt who became the first chairman of the Kreisau foundation, she was "Kreisau's guardian angel."

"New Kreisau profits immensely from the fact that the Moltke family is behind the effort," Mr. Telschow says. "It opens doors and sources that might otherwise be closed."

"Caspar continues a mission strongly associated with his mother," says Bürger, the Berlin pastor. "It is good and important because, through Freya, Konrad, and now Caspar, the name Helmuth James von Moltke stands for an open future for Europe and a world that hinges on the rule of law and on the protection of human rights."

In the 1920s young Helmuth James had tried to improve horrendous conditions in Silesia's coal mines by living and working there as part of a youth camp organized by his teacher, Eugene Rosenstock-Huessy.

The experience taught him the value of sharing viewpoints and making compromises to bring about change. During the Third Reich, his youth camp friends – aristocrats and trade unionists, Protestants and Roman Catholics – made up the Kreisau Circle. "If I don't do something that sustains my hope. I won't be able to stand it," Helmuth James wrote to Freya.

As counselor to the German Army's high command, Helmuth James fought for compliance with international law and the fair treatment of prisoners. He wrote about the psychological suffering of German soldiers involved in mass killings of Jews and Eastern Europeans. "His idea was that the criminals of the Nazi periods should be judged by an international court," Moltke says.

Inside the whitewashed palace recently, 80 high school pupils from Slovakia, Afghanistan, Germany, and the Czech Republic were putting into practice Helmuth James's ideals. They reenacted the roles of prosecutors, journalists, and judges in three of the world's most famous international criminal trials – Nuremberg, Yugoslavia, and Rwanda – by participating in the center's Model International Criminal Court.

German 12th-grader Tamta Kalandarishvili served as prosecutor in the case of Drazen Erdemovic, a Bosnian Croat soldier convicted in the massacre at Srebrenica, Bosnia. The role made her understand "why we need international institutions, why trying people [in court] is important in a constitutional state," she says.

For others, like Ajmal Rasouli from Kabul, Afghanistan, witnessing "fair trials, how criminals can actually be punished ... gives me hope that one day the people of Afghanistan will see that criminals are brought to justice as well."

Rebekka Rabiega, a teacher from Wroclaw, Poland (named Breslau until 1945), calls the project a "step away" from war. "We might think that European reconciliation is a done fact, but it's a never-ending story," says Ms. Rabiega.

Hava Kohav Beller, a German-born film producer, made a 1992 Oscar-nominated documentary "The Restless Conscience" that documents the Kreisau Circle's Nazi resistance.

The message of Kreisau, she says from New York, where she now works, "is universal, going beyond the Western European 'club' to also embrace the other regions of the world, where, alas, violence and strife and deadly divisions are still rampant."

[Editor's note:The original version of this story incorrectly stated that Moltke's ancestor acquired the estate as a thank you for help in winning a war against Prussia. The war was against Austria.]

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